• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제16권8호
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• pp.756-761
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• 2004

Since the use of CFC and HCFC refrigerants are to be restricted due to the depletion of ozone layer, this experiment applies the NH$_3$ gas to study the performance characteristics from the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 14.5 bar to 16.0 bar by 0.5 bar and for superheat temperature from $0^{\circ}C$ to 1$0^{\circ}C$ by 1$^{\circ}C$ at each condensing pressure. As a result of experiment, when the superheat temperature is 1$^{\circ}C$ at each condensing pressure, the refrigeration system has the highest performance.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1334-1339
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• 2004

Nowadays CFCs and HCFCs refrigerants are restricted because it cause depletion of ozone layer. Accordingly, this experiment apply the $NH_3$ gas and not CFCs and HCFCs for refrigerant to study the performance characteristic from the superheat control and improve the energy efficiency from the high performance. The condensing pressure of refrigeration system is increased from 14.5bar to 16bar by 0.5bar and superheat temperature is increased from $0^{\circ}C$ to $10^{\circ}C$ by $1^{\circ}C$ at each condensing pressure. As the result of experiment, when the superheat temperature is $1^{\circ}C$ at each condensing pressure, the refrigeration system has the high performance.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.60-65
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• 2005

Nowadays HCFCs refrigerant are restricted because it cause depletion of ozone layer. However, natural gases such as ammonia as an organic compound, propane and propylene as hydrocarbon are easy and cheap to obtain as well as environmental. Accordingly, this experiment apply the $NH_3$ and R22 to study the performance characteristic from the superheat control and compare the energy efficiency of two refrigerants from the high performance. The condensing pressure of refrigeration system is increased from 15bar to 16bar and degree of superheat is increased from 0 to $10^{\circ}C$ at each condensing pressure. As the result of experiment, when comparing the each COP, we knew the $NH_3$ is suitable as the alternative refrigerant of the R22.

• Journal of Photoscience
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• 제9권3호
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• pp.37-40
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• 2002

Astronauts are constantly exposed to space radiation at a low-dose rate during long-tenn stays in space. Therefore, it is important to determine correctly the biological effects of space radiation on human health. Space radiations contain various kinds of different energy particles, especially high linear energy transfer (LET) particles. Therefore, we have to study the relative biological effectiveness (RBE) of space radiation under microgravity environment which may change RBE from a stress for cells. Furthermore, the research about space radiation might give us useful information about birth and evolution of life on the earth. We also can realize the importance of preventing the ozone layer from depletion by use of exposure equipment to sunlight at International Space Station (ISS).

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 한국화재소방학회 1997년도 International Symposium on Fire Science and Technology
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• pp.550-557
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• 1997

Production of so-called Halon fire extinguishing agents has been prohibited since January 1994 because of their ozone depletion potential, To replace them, several hydrofluorocarbons and fluorocarbons have been developed and utilized. A number of studies on flame extinguishing concentrations and flammability peak concentrations of them have been done. Although there was enough information for practical purpose, more knowledge on fire extinguishing characteristics of them should be attained for efficient use of them. In this study, peak concentrations of methane/air mixtures with gaseous halogenated hydrocarbons were measured at elevated temperature, because the former studies were done at room temperature and temperature of a fire room can be higher than usual. Measurement was done at $200^{\circ}C$, because measuring system could not endure higher temperature. This study revealed that peak concentrations of halogenated hydrocarbons differed little at elevated temperature. The halogenated hydrocarbons have almost the same fire extinguishing ability as Halon 1301.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권3호
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• pp.100-106
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• 2009

As an effort to prevent environmental problems caused by ozone depletion and global warming, alternative refrigerants are being developed, and one of the candidates is carbon dioxide. To overcome slightly low efficiency of $CO_2$ refrigeration system, air-conditioning cycle using an ejector was suggested. Ejector compensates throttling loss in an expansion device by reducing compression work. In this study, the ejector refrigeration cycle using $CO_2$ as a refrigerant is investigated to understand the effect of the mixing section diameter and refrigerant charge amount on the performance. If mixing section diameter is too large or too small, either cases show low performance. The optimum refrigerant charge amount which gives the best performance is found for standard operating conditions. The air-conditioning cycle was analyzed for several operating conditions.

• Journal of Korean Society of Environmental Engineers
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• 제39권12호
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• pp.698-705
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• 2017

Environmental impact of a mobile phone charger containing recycled plastic was quantified using LCA and the environmental benefits from the use of recycled and virgin plastic were compared. The assessment considers potential environmental impacts across the whole life cycle of the charger including; pre-manufacturing; manufacturing; distribution; product use; and end-of-life stages and quantified six environmental impact categories; Abiotic depletion; Acidification; Eutrophication; Global warming; Ozone layer depletion; and Photochemical oxidants creation. The study showed that the environmental impacts of the use stage accounted for 94.4% and 70% in the resource depletion and global warming impact categories, respectively, and the environmental impacts of the pre - manufacturing stage accounted for more than 98% in the other impact categories. The main cause of the environmental impacts in the use stage was electricity consumed by the charger. The main cause in the pre-manufacturing stage was PBA (Printed Board Assembly) and external case manufacturing. In order to quantify the environmental benefits of recycled PC (Polycarbonate) in the exterior case, the environmental impacts of 1 kg production of recycled PC and virgin PC were evaluated. The environmental impact on the abiotic depletion of the recycled PC is estimated to be 30% compared to the virgin PC, and the impacts on the other impact categories of the recycled PC were less than 5% of the virgin plastic. Sensitivity analysis was performed for 12 items including site data and assumptions made. The sensitivity of each item was less than 10%. The results of this study confirm that designing compact and light PBA, improving charging efficiency, and use of recycled plastic are important design factors to reduce the environmental impact of a charger.

• Clean Technology
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• 제28권3호
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• pp.203-209
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• 2022

An environmental evaluation was conducted by employing LCA methodology for a mechanical seal manufacturing process that uses recycled silicon recovered from end-of-cycle PV modules. The recycled silicon was purified and reacted with carbon to synthesize β-SiC particles. Then the particles underwent compression molding, calcination and heat treatment to produce a product. Field data were collected and the potential environmental impacts of each stage were calculated using the LCI DB of the Ministry of Environment. The assessment was based on 6 categories, which were abiotic resource depletion, acidification, eutrophication, global warming, ozone depletion and photochemical oxidant creation. The environmental impacts by category were 45 kg CO₂ for global warming and 2.23 kg C₂H₄ for photochemical oxide creation, and the overall environmental impact by photochemical oxide creation, resource depletion and global warming had a high contribution of 98.7% based on weighted analysis. The wet process of fine grinding and mixing the raw silicon and carbon, and SiC granulation were major factors that caused the environmental impacts. These impacts need to be reduced by converting to a dry process and using a system to recover and reuse the solvent emitted to the atmosphere. It was analyzed that the environmental impacts of resource depletion and global warming decreased by 53.9% and 60.7%, respectively, by recycling silicon from end-of-cycle PV modules. Weighted analysis showed that the overall environmental impact decreased by 27%, and the LCA analysis confirmed that recycling waste modules could be a major means of resource saving and realizing carbon neutrality.

• Korean Journal of Construction Engineering and Management
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• 제16권3호
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• pp.49-58
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• 2015

In order to determine how much a new green building reduce the environmental impacts, it is necessary to establish the reference target for comparison. Therefore, this study aims to establish the reference target by evaluating the environmental impacts of existing buildings. To ensure this end, this study evaluated the environmental impacts(Global warming potential, ozone layer depletion potential, acidification potential, eutrophication potential, photochemical ozone creation potential, and abiotic depletion potential) of 17 existing elementary school buildings, which are located in Seoul, Busan, Daegu, and Gwangju, by using the hybrid LCA model. As a result, the environmental impacts of the case buildings were clearly distinguished in different regions. Therefore, this study presented the reference targets which are appropriate to each region. For example, the reference targets for global warming potential, which can be used in Seoul, Busan, Daegu, and Gwangju, are 3.76E+03, 1.90E+03, 2.63E+03, $2.81E+03kg-CO_2\;eq./m^2$, respectively. The presented reference targets are expected to be useful for understanding how much environmental impacts can be reduced when a new green school building is constructed.

• Clean Technology
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• 제21권1호
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• pp.33-38
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• 2015

In this research, life cycle inventory database (LCI DB) was developed for liquid CO₂ employing life cycle assessment (LCA) methodology. As are result of characterization and normalization process, production of liquid CO₂ puts on environmental impact in the order of resource depletion, global warming, acidification, eutrophication and photochemical oxidation, and among a wide variety of input, electricity contributes in most of the impact categories. Air emission plays a key role in the acidification and eutrophication while ammonia affects most on the ozone depletion. It is anticipated that development of liquid CO₂ LCI DB makes it possible for national environmental strategies to be more activated including environmental labeling scheme.